1. Field of the Invention
The present invention relates to armor structures, and more particularly to lightweight, high strength structural armor components requiring minimum space allocation, and having improved capability for surviving high energy blast loads and impeding penetration therethrough by high speed projectiles.
2. Description of the Related Art
Conventional armor plating is typically made of ceramic materials, metallic materials, high-elongation organic materials, or a combination of two or more thereof. An example of conventional armor, is disclosed in U.S. Pat. No. 4,404,889 issued to Miguel. The '889 armor includes layers of high density steel honeycomb, balsa wood, and ballistic resistant nylon sandwiched in various arrangements between outer layers of steel armor plate.
An improvement in lightweight structural armor is disclosed in U.S. Pat. No. 5,435,226 issued to Fred McQuilkin and assigned to Rockwell International Corporation. The '226 armor employs a 3-sheet single truss core design with abrasive or laminate materials provided in the interior cells or flutes of the truss members. The abrasive or laminate materials are held in place by inflating bladders during the bonding process, which are later removed.
The single truss axis of the '226 design provides energy absorption from the blast wave concentrated primarily in one axis, which can possibly allow large structural deflections in the axis transverse to the truss core member axis. Also, fragment energy dissipation is accomplished by laminates inserted into the truss member flutes which are oriented in a single axis only. A fragment can possibly migrate between the laminate inserts and thus reduce the laminate energy absorption capability.
Ceramic materials offer significant efficiency in defeating armor piercing projectiles at the lowest weight per square foot of surface area. The ceramic armor sections are generally mounted on a tough support layer such as glass-reinforced plastics. Boron carbide, silicon carbide and alumina are ceramics which are commonly used in armor plating.
However, ceramic plates have the serious drawback of being unable to sustain and defeat multiple hits by armor piercing projectiles. Because relatively large sections of ceramic material must be used to stop these projectiles and because these sections shatter completely when hit by a projectile, the ceramic armor is unable to defeat a second projectile impacting close to the preceding impact. Moreover, sympathetic shattering of adjacent ceramic sections usually occurs, still further increasing the danger of penetration by multiple rounds.
In addition, ceramic armors are difficult and costly to manufacture; not only are very high manufacturing temperatures required, but also processing is time consuming because very slow cooling is necessary to avoid cracking. Also, ceramic armor cannot carry significant structural loads, and therefore adds parasitic weight to the load carrying structure.
Metallic materials have been implemented for light weight armor applications because they possess excellent ability to defeat multiple, closely spaced impacts of armor piercing projectiles. However, this class of materials is often far heavier than desired and difficult to fabricate into intricate contours. Moreover, the weight of metallic materials have typically precluded their extensive use in such lightweight mobile weapons systems as helicopters and small water craft.